Jan Kudlacek died November 25, 2017 at the age of 89 years
Vaclav Kudlacek - son, died April 24, 2018 at the age of 53
I don't know of any other heirs.
These pages were created during the life of Jan Kudláček and he sincerely enjoyed them. They succeeded in completing them and launching them with the help of Václav Kudláček, who was the son of Jan and devoted them as a tribute to his father, his work and especially to his readers and admirers.
Vaclav Kudlaček was also planning to possibility for sale reproductions of illustrations and originals in the upcoming, unpublished section, "Selling Illustrations". The publication of this option has not occurred and so I do not know if the estate administrator will offer this opportunity to the public.